Vehicle suspension systems give passengers a comfortable ride typically by supporting the vehicle and responding to road bumps, road irregularities by moving up and down. But these motions induce undue oscillations or vibrations and a damper or shock absorber is used to dampen out the vibrations. Typical shock absorbers function by dissipating or absorbing the unwanted energy.
There are several types of shock absorbers. Some work on hydraulics while others work on pneumatic or eddy current types of damping. Pneumatic shock absorbers convert kinetic energy from road bumps or vibrations into heat by heating the surrounding air while hydraulic type shock absorbers function similarly by converting the kinetic energy into heat for absorption by a fluid, such as oil.
Vehicle efficiency can be increased if this wasted energy can be harvested and converted into useful energy. With the advent of gas-electric hybrids and electric vehicles any regenerative energy which can be harvested from a car can extend the range of the car for a given battery charge. Some literature indicates that about 15% of energy generated by a vehicle is wasted due to damping.
Dampers are also used in vehicles in other locations such as in the engine mounts and/or seat mounts. In electric vehicles and hybrid vehicles dampers are also used in battery mounts. All these different types of dampers convert vibrational energy into heat or other kinds of wasted energy.
As a vehicle travels, energy in the form of bumps or shocks is typically generated as the suspension system absorbs such energy from the interface against the road; however, such energy is usually dissipated quickly. Harnessing this wasted energy by converting it into useful electrical energy is a way to improve the efficiency of the vehicles. Power generation from dampers has not been significantly developed or explored. Conventional devices typically suffer from practical limitations. For example, U.S. Pat. Nos. 4,500,827; 5,578,877; and 5,347,186 all describe different embodiments of electromagnetic linear generators which convert road vibration energy into electrical energy by using the principle of electromagnetism. Another example is described in U.S. Pat. No. 6,952,060 which discloses an electromagnetic linear generator which converts the road vibrational energy into electrical energy from the relative motion of an assembly of coil windings array and magnet array. U.S. Pat. No. 6,920,951 describes a power screw type of regenerative damper which uses a rotor and a stator. Yet another example is shown in U.S. Pat. App. 2009/0260935 A1 which discloses a regenerative shock absorber which compresses a hydraulic fluid in a cylinder by a piston which moves corresponding to the road vibration. The fluid then passes through a hydraulic motor which converts rotary motion of the shaft into electrical energy. This device also uses electric generators such as permanent magnet systems for converting the rotary motion into useful electrical energy.
However, conventional devices usually add to the weight of the vehicle and may negatively influence any gains in energy efficiency and may also potentially increase the cost of the vehicle. Dielectric elastomer materials are transducers which can be used in both actuation mode and energy generation mode. In U.S. Pat. App. 2007/0257491 A 1, marine devices which can convert the mechanical energy present in waves into electrical energy are described. Dielectric elastomer generators are used. In U.S. Pat. No. 6,768,246, designs and methods for converting energy generated from biologically-derived activities such as walking, running, etc. into electrical energy using dielectric elastomer generators are described. However, application of dielectric elastomer based devices for energy generation from automotive sources and other industrial and household sources has not been explored significantly. All patents and patent applications described herein are incorporated herein by reference in their entirety.